In polymer processing and mixing equipment new feed material falls from a hopper into the processing equipment. The present invention discloses a new type of hopper that obviates some of the undesirable features attending such existing methods and apparatus.
Recently, a new type of mixing extruder has been developed which is commonly known as the elastic melt extruder. This apparatus comprises the subject matter of U.S. Pat. No. 3,046,609, U.S. Pat. No. 3,545,041 and U.S. Pat. No. 3,790,328 all issued to the present inventor on July 31, 1962, Dec. 8, 1970, and Feb. 5, 1974, respectively. The present invention provides a means of introducing new feed material into elastic melt extruders that overcomes some of the undesirable features of the current apparatus.
In addition, the disclosed invention may be used to feed material into the processing apparatus described in applicant's pending application U.S. Ser. No. 358,656, filed May 9, 1973, now U.S. Pat. No. 3,863,905. It should be noted the disclosed invention may be used advantageously to feed material into other types of processing equipment.
Although the above identified processing machines have proven to be highly useful and desirable pieces of equipment for melting, mixing, devolatizing and extending polymer materials, some difficulty has been encountered in the introduction of new feed material in these machines.
Unless some means is provided to facilitate the introduction of new feed material into the processing equipment and to control the rate of input of new feed material, the output rate of the processing equipment varies from time to time in an undesirable manner. This variation in output rate is caused by material bridging in the hopper thereby cutting off the input of new material or by hot, melted material flowing backwards into the hopper when too much feed material has entered the processing equipment. This hot melted material can plug or block the subsequent flow of new feed material from the hopper.
In addition, the current hoppers are designed in a manner that causes any volatile material resulting from the melting of the polymer to flow backwards through the hopper thereby contaminating the new feed material. It is an objective of the present invention to prevent such contamination.
Past efforts in devising apparatus for properly introducing feed materials into polymer processing equipment have resulted in hopper designs that require additional power driven apparatus. Examples of current practice include the use of power rotated augers in the hopper and power activated rams to push material from the hopper. The present invention in some of its manifestations require no external source of power.
It is desirable if an improved apparatus and method were provided for introduction of feed material into processing equipment that would obviate the above discussed problems.